*
*/
@Test
public void secondDerivativeFiniteDifferenceTest() {
final PiecewisePolynomialInterpolator[] interps = new PiecewisePolynomialInterpolator[] {new NaturalSplineInterpolator(), new CubicSplineInterpolator(),
new PiecewiseCubicHermiteSplineInterpolator(), new ConstrainedCubicSplineInterpolator(), new SemiLocalCubicSplineInterpolator() };
final int nInterps = interps.length;
for (int k = 0; k < nInterps; ++k) {
final double[] xValues = new double[] {1., 2.8, 3.1, 5.9, 10., 16. };
final double[] yValues = new double[] {1., 2., 3., -2., 5., -5. };
final int nData = xValues.length;